54LS256 DM74LS256 Dual 4-Bit Addressable Latch General Description The LS256 is a dual 4-bit addressable latch with common control inputs these include two Address inputs (A0 A1) an active LOW enable input (E) and an active LOW Clear input (CL) Each latch has a Data input (D) and four outputs (Q0 Q3) When the Enable (E) is HIGH and the Clear input (CL) is LOW all outputs (Q0 Q3) are LOW Dual 4-channel demultiplexing occurs when the CL and E are both LOW When CL is HIGH and E is LOW the selected output (Q0 Q3) determined by the Address inputs follows D When the E goes HIGH the contents of the latch are stored When operating in the addressable latch mode (E e LOW CL e HIGH) changing more than one bit of the Address (A0 A1) Connection Diagram Dual-In-Line Package June 1989 could impose a transient wrong address Therefore this should be done only while in the memory mode (E e CL e HIGH) Features Logic Symbol Serial-to-parallel capability Output from each storage bit available Random (addressable) data entry Easily expandable Active low common clear 54LS256 DM74LS256 Dual 4-Bit Addressable Latch TL F 9823 1 Order Number 54LS256DMQB 54LS256FMQB or DM74LS256N See NS Package Number J16A N16E or W16A V CC e Pin 16 GND e Pin 8 TL F 9823 2 Pin Names A0 A1 D a D b E CL Q0 a Q 3 a Q0 b Q 3 b Description Common Address Inputs Data Inputs Common Enable Input (Active LOW) Conditional Clear Input (Active LOW) Side A Latch Outputs Side B Latch Outputs C1995 National Semiconductor Corporation TL F 9823 RRD-B30M115 Printed in U S A
Truth Table Logic Diagram Inputs Outputs CL E A0 A1 Q0 Q1 Q2 Q3 L H X X L L L L Clear Mode L L L L D L L L Demultiplex L L H L L D L L L L L H L L D L L L H H L L L D H H X X Q tb1 Q tb1 Q tb1 Q tb1 Memory H L L L D Q tb1 Q tb1 Q tb1 Addressable H L H L Q tb1 D Q tb1 Q tb1 Latch H L L H Q tb1 Q tb1 D Q tb1 H L H H Q tb1 Q tb1 Q tb1 D tb1 e Bit time before address change or rising edge of E H e HIGH Voltage Level L e LOW Voltage Level X e Immaterial Mode Selection E CL Mode L H Addressable Latch H H Memory L L Active HIGH 4-Channel Demultiplexers H L Clear TL F 9823 3 2
Absolute Maximum Ratings (Note) If Military Aerospace specified devices are required please contact the National Semiconductor Sales Office Distributors for availability and specifications Supply Voltage 7V Input Voltage 7V Operating Free Air Temperature Range 54LS b55 Ctoa125 C DM74LS 0 Ctoa70 C Storage Temperature Range b65 Ctoa150 C Recommended Operating Conditions Symbol Parameter 54LS256 Note The Absolute Maximum Ratings are those values beyond which the safety of the device cannot be guaranteed The device should not be operated at these limits The parametric values defined in the Electrical Characteristics table are not guaranteed at the absolute maximum ratings The Recommended Operating Conditions table will define the conditions for actual device operation DM74LS256 Min Nom Max Min Nom Max V CC Supply Voltage 4 5 5 5 5 4 75 5 5 25 V V IH High Level Input Voltage 2 2 V V IL Low Level Input Voltage 0 7 0 8 V I OH High Level Output Current b0 4 b0 4 I OL Low Level Output Current 4 8 T A Free Air Operating Temperature b55 125 0 70 C t s (H) Setup Time HIGH D n to E 20 20 ns t h (H) Hold Time HIGH D n to E 0 0 ns t s (L) Setup Time LOW D n to E 15 15 ns t h (L) Hold Time LOW D n to E 0 0 ns t s (H) t s (L) Setup Time HIGH or LOW A n to E Units 0 0 ns t w (L) E Pulse Width LOW 17 17 ns Electrical Characteristics Over recommended operating free air temperature range (unless otherwise noted) Symbol Parameter Conditions Min Typ (Note 1) V I Input Clamp Voltage V CC e Min I I eb18 b1 5 V V OH High Level Output V CC e Min I OH e Max 54LS 2 5 Voltage V IL e Max DM74 2 7 3 4 V OL Low Level Output V CC e Min I OL e Max 54LS 0 4 Voltage V IH e Min DM74 0 35 0 5 V Max I OL e 4 V CC e Min DM74 0 25 0 4 I I Input Current Max V CC e Max V I e 10V Inputs 0 1 Input Voltage E 0 2 I IH High Level Input Current V CC e Max V I e 2 7V Inputs 20 E 40 I IL Low Level Input Current V CC e Max V I e 0 4V Inputs b0 4 I OS Short Circuit V CC e Max 54LS b20 b100 Output Current (Note 2) DM74 b20 b100 I CC Supply Current V CC e Max 25 Note 1 All typicals are at V CC e 5V T A e 25 C Note 2 Not more than one output should be shorted at a time and the duration should not exceed one second 3 E b0 8 Units V
Switching Characteristics V CC ea5 0V T A ea25 C (See Section 1 for waveforms and load configurations) R L e 2kX Symbol Parameter C L e 15 pf Units Max t PLH Propagation Delay 27 t PHL E to Q n 24 ns t PLH Propagation Delay 30 t PHL D n to Q n 20 t PLH Propagation Delay 30 t PHL A n to Q n 29 t PLH Propagation Delay CL to Q n ns ns 18 ns 4
Physical Dimensions inches (millimeters) 16-Lead Ceramic Dual-In-Line Package (J) Order Number 54LS256DMQB NS Package Number J16A 16-Lead Molded Dual-In-Line Package (N) Order Number DM74LS256N NS Package Number N16E 5
54LS256 DM74LS256 Dual 4-Bit Addressable Latch Physical Dimensions inches (millimeters) (Continued) 16-Lead Ceramic Flat Package (W) Order Number 54LS256FMQB NS Package Number W16A LIFE SUPPORT POLIC NATIONAL S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF NATIONAL SEMICONDUCTOR CORPORATION As used herein 1 Life support devices or systems are devices or 2 A critical component is any component of a life systems which (a) are intended for surgical implant support device or system whose failure to perform can into the body or (b) support or sustain life and whose be reasonably expected to cause the failure of the life failure to perform when properly used in accordance support device or system or to affect its safety or with instructions for use provided in the labeling can effectiveness be reasonably expected to result in a significant injury to the user National Semiconductor National Semiconductor National Semiconductor National Semiconductor Corporation Europe Hong Kong Ltd Japan Ltd 1111 West Bardin Road Fax (a49) 0-180-530 85 86 13th Floor Straight Block Tel 81-043-299-2309 Arlington TX 76017 Email cnjwge tevm2 nsc com Ocean Centre 5 Canton Rd Fax 81-043-299-2408 Tel 1(800) 272-9959 Deutsch Tel (a49) 0-180-530 85 85 Tsimshatsui Kowloon Fax 1(800) 737-7018 English Tel (a49) 0-180-532 78 32 Hong Kong Fran ais Tel (a49) 0-180-532 93 58 Tel (852) 2737-1600 Italiano Tel (a49) 0-180-534 16 80 Fax (852) 2736-9960 National does not assume any responsibility for use of any circuitry described no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications